Simulation of bushfire impacts on runoff in a typical small-sized catchment

The Mcmahons Creek catchment is located in southeast Australia, where a bushfire occurred in February 1983.The catchment is selected for a case study to investigate the bushfire impacts on the streamflow regime.The Australian Water Resources Assessment System Landscape (AWRA-L) model and the Chinese Xin'anjiang model are used for hydrological simulations on the catchment.The impact of bushfire on the streamflow regime can be measured by the difference in runoff before and after the occurrence of the bushfire.The result shows that the average of annual runoff in the first 14 years (1983—1997) after the bushfire is increased by 140 mm for the AWRA-L model, and 123 mm for the Xin'anjiang model.The corresponding increases are 33% and 29%, respectively.This is compared to that before the bushfire averaging for the period 1974—1982.During the period 1998—2004 (or the second 14 years after the bushfire), another increase of 43 mm (10%) is obtained for the AWRA-L model.While for the Xin'anjiang model, the extra amount in annual runoff is 33 mm (8%).The study demonstrates that although there is a substantial increase in annual runoff in the immediate post-fire period, the increment of runoff generation will be gradually reduced due to the recovering of plantations.Logging is an important factor for the runoff increase in the first 14 years after the bushfire.The study also provides a reference to the practice of water resources management in forest catchments.